Superhydrophobic and Water-Repellent Coatings with Dual-Scale Roughness Based on Waterborne MXene Nanocomposites

The development of superhydrophobic and water-repellent surfaces utilizing a facile, economic and environmental-friendly way constitute an important scientific challenge since these materials find applications in a great number of industrial sectors as manufacturing, healthcare, and everyday consumer products. In this work, two-dimensional layered MXenes are utilized as functional additives for the development of superhydrophobic and water-repellent coatings prepared using waterborne nanocomposite formulations, which contain a low surface energy, short-chain perfluoroalkyl silanol, to provide the appropriate hydrophobicity; the nanoadditives are introduced to create the necessary surface roughness. While traditional methods typically employ 0D nanoparticles to achieve surface nanostructuring, the flake-like structure of Ti₃C₂T _x MXenes introduces roughness that extends into the micron-scale. Different smooth substrates were coated by a one-step spraying process and the surface properties were investigated as a function of the additive content. Moreover, ternary nanocomposite coatings were developed with MXenes and alumina nanoparticles by a single-step spraying of an aqueous suspension. This combination results in hierarchical surface structures (with micrometer- and nanometer-scale roughness), achieving excellent water repellence with significantly lower additive concentration than the one needed when single-type of nanoadditives were used. Due to the low Ti₃C₂T _x MXene content, the use of our approach extends beyond dark-colored applications, even in cases where the aesthetic result is critical. The nanohybrid coated surfaces exhibited mechanical and chemical durability, retaining their hydrophobicity after repeated abrasion cycles and under extreme pH conditions (pH 2 or 13). This study highlights the potential of MXenes as an innovative additive for next-generation water-repellent coatings.